Sending some timestamp along with a Prometheus alert text is sometimes very useful to gain better awareness. For example, when exactly will a TLS certificate expire, instdead of some generic text like "TLS certificate will expire in less than x days": groups: - name: Blackbox rules rules: - alert: SSLCertExpiringSoon

We started out with rather rigid way of defining alerts. Using custom labels, which are defined within the alert rule, we made it simpler.